Fig. 4.

Targeted fluorescence uptake versus dual-reporter imaging within 1 h of reporter injection. The $\text{mean}\pm \text{standard}$ error targeted fluorescence uptake tumor contrast-to-noise ratio (CNR) within 1 h of reporter injection is presented in (a) for each tumor group ($A431=\mathrm{red}$; $U251=\mathrm{blue}$; $9L\text{-}\mathrm{GFP}=\mathrm{black}$; $\text{blocked U251\hspace{0.17em}}=\text{dark yellow}$). The $\text{mean}\pm \text{standard}$ error tumor CNR determined by the dual-reporter approach for the same tumor groups as in (a) is presented in (b). The correlation between the average dual-reporter image value of the tumor in each mouse at 20 min and 1 h after reporter injection and the corresponding binding potential (an in vivo marker of receptor expression) are presented in (c) and (d), respectively. Data points from each tumor line are color-coded to match the data in (a) and (b). The slope of the 20-min correlation was $0.61\pm 0.12$ ($r=0.89$, $P<0.05$), and the 1-h correlation was $0.68\pm 0.05$ ($r=0.94$, $P<0.01$).